Year	current US$
2010	33.82830407
2011	32.56623409
2012	31.21323293
2013	29.79671044
2014	28.41852566
2015	27.10101607
2016	25.43845392
2017	9.73139564
2018	10.08352011
2019	4.97846005
2020	5.2745668
2021	6.4337428